Automation and robotization of an assembly process in any industry is desirable for the improvement of productivity and for cost reduction. This is particularly true in a complex manufacturing process such as the manufacture of television receivers or video monitors. The present invention is concerned with the automation, in particular the robotization, of one step in this process, i.e. the assembly of the kinescope to the external magnetic deflection yoke (hereinafter "yoke").
In a television receiver or video monitor, the yoke, which is an assembly of coils, surrounds the neck portion of the kinescope, i.e. the cathode ray tube or picture tube. In the conventional method of assembling a yoke and kinescope, the yoke is positioned on the neck of the kinescope for maximum color purity and convergence and manually secured thereto with a clamp. The yoke is then tilted slightly with respect to the kinescope until maximum focusing is achieved and self-adhering rubber wedges are manually inserted between the yoke and the kinescope to maintain the correct tilt. These operations require about 0.75 man-hours to perform.
It is readily apparent that an adhesive which would permit the assembly and proper relative alignment of the kinescope and the yoke by an automated process, particularly utilizing robotics, would represent a significant advantage in cost and time savings as well as improving the uniformity and performance of the assembled display. There is, however, a substantial list of critical criteria which an adhesive must meet in order to facilitate robotizing of the kinescope/yoke assembly process.
First, the adhesive must have particular setting characteristics. A suitable adhesive cannot set instantly since that would not permit any final fine alignment of the kinescope relative to the yoke and would not permit transfer of the adhesive dispensing apparatus to the next assembly without clogging of the dispenser tubes. On the other hand, in order that the process can be cost effective, the adhesive must firmly set within about one minute so that the assembly apparatus, or robot, can release the assembly and rapidly engage the next.
A suitable adhesive must be compatible with and adhere well to the various materials to be contacted in the assembly, i.e. magnetic wires, a glass funnel, plastic casings and the like. A suitable adhesive must also maintain excellent dimensional stability so that the alignment of the parts will not change to the detriment of convergence and color purity in the final product. It is necessary that the adhesive not undergo more than a two percent change in dimension on curing or over the service life of the assembled receiver or monitor.
A suitable adhesive must be sufficiently thixotropic to maintain a uniform dispersion of the filler particles and, more importantly, to maintain the shape of the dispensed adhesive during curing in the space between the yoke and the kinescope which can vary between about 10 and 2000 mils.
In addition to the foregoing, a suitable adhesive must be fire-resistant, shock resistant to 35 g of impact which might be encountered in shipping; able to withstand thermal cycling of from -25.degree. C. to 85.degree. C., which is the possible operating temperature range of a television set, and be reasonable in cost. The adhesives provided in accordance with this invention meet all of these required criteria.